Protect PDF
Process your PDF files online quickly and securely.
Drag & drop your PDF here
or click to select file
User Guide
Add the document
Upload the PDF you want to lock. This tool accepts larger files than most on the site — up to 100 MB — so full scanned reports and bundles are within reach.
Choose a password you can transmit safely
The strength of the encryption is irrelevant if the password travels badly. A long passphrase of a few unrelated words beats a short string of substituted characters, and it survives being read aloud over the phone, which is often how it will need to be shared.
Protect the PDF
Run the tool and download the encrypted copy. Your original is untouched — what comes back is a new, locked version, so there is no risk of ending up with nothing you can open.
Test it, then send the password separately
Open the downloaded file and confirm it asks for the password and accepts it. Then send the document and the password by different routes — the file by email, the password by message or phone. A password in the same email as the attachment protects against nothing.
About the Protect PDF Tool
Password-protecting a PDF encrypts its contents. This is real cryptography, not a flag a reader can be persuaded to ignore, and it is the right control for a document that will travel by email or sit in shared storage.
What actually happens to the file
The document’s streams — the instructions that draw the text and images — are encrypted, and a key derived from your password is required to decrypt them before anything can be rendered. Modern PDF encryption uses AES, the same family of ciphers used for disk encryption and secure connections. A reader without the password cannot display the file, extract its text, or recover its images, because it does not have the bytes.
Two kinds of PDF password, and only one really works
The PDF format defines a user password, needed to open the document at all, and an owner password, which sets permission flags for printing, copying and editing. The distinction matters: the open password is enforced by mathematics, while the permission flags are enforced only by the reader’s good manners. Plenty of software ignores them entirely. If something must not be read, use an open password; do not rely on a “no printing” flag to stop a determined recipient.
Choosing a password worth the encryption
The cipher is not the weak point — transmission and memorability are. A passphrase of four unrelated words is far harder to attack than eight characters of substituted punctuation, and it survives being read aloud over the phone, which is often how it must be shared. Avoid anything derived from the document itself: the invoice number, the client’s name, the date. Those are the first things anyone would try.
There is no recovery
A PDF whose password is lost cannot be opened by us or by anyone else. That is the entire point of encrypting it. Record the password in a password manager before you send the file, and send it by a different channel from the document — a locked file and its key in the same email protects against nothing.
Practical notes
This tool accepts files up to 100 MB, more than the general converters, so full scanned bundles can be protected in one piece. Your original is untouched; you receive a new encrypted copy. Encryption is applied on a server, so for an exceptionally sensitive document the safest route remains a tool on a machine you control — true of every online service, this one included.
Frequently Asked Questions
What happens if I forget the password?
The file cannot be opened, by you or by us. That is what encryption means — there is no master key and no reset. Store the password in a password manager before you send the document anywhere.
Why does this tool accept 100 MB when others stop at 10?
Security tools are configured with a higher ceiling than the general converters, so large scanned bundles can be protected in one piece rather than split first. The limit is applied per file.
Can the recipient remove the password later?
Yes, if they have it. With the password they can open the document and save an unprotected copy — the Unlock PDF tool does exactly that. Encryption controls who can get in, not what they do afterwards.
Does this stop printing or copying text?
This adds an open password, which governs access to the document as a whole. Permission settings that attempt to restrict printing or copying are a different mechanism, and one that many readers honour only by convention.
Should I send the password in the same email?
No. A locked file and its key in one message is equivalent to sending the file unlocked, since anyone who intercepts the message has both. Use a different channel for the password.
Is my original file modified?
No. You get back a new encrypted copy and keep the original exactly as it was, so a mistyped password costs you a re-run rather than the document.
